1. Field of the Invention
The present invention relates generally to networks and, more particularly, to systems and methods for detecting the presence of nodes in wireless networks.
2. Description of Related Art
The use of ad hoc wireless networks has increased in recent years. An ad hoc wireless network typically includes several wireless, sometimes mobile, nodes. In such a network, all of the nodes may be equipped with wireless communications transceivers. Some of the nodes (e.g., routers) may be designed to perform network routing functions while other nodes may be merely sources or destinations for data traffic.
All of the nodes in the network may execute a set of algorithms and perform a set of networking protocols that enable the nodes to find each other and determine paths through the network for data traffic from source to destination(s). The algorithms/protocols also enable the nodes to detect and repair ruptures in the network as nodes move, as nodes fail, as battery power changes, as communications path characteristics change over time, and so forth.
Conventional ad hoc wireless networks employ “beacons” as a way in which network nodes can perform neighbor discovery (i.e., locate other nearby nodes). A beacon is a transmission that can be generated by one node and received by some or all of the nodes within a transmission range. In other words, the beacon is a broadcast, rather than a transmission to any particular node. In some networks, all of the nodes may beacon, while in other networks, only a subset of the nodes may beacon. Beacons serve to alert a given receiving node that there may be one or more other (i.e., transmitting) nodes in their proximity.
Beacons typically include an identification of the node that is transmitting the beacon, forward error correction information, and other information based on the type of wireless networking protocols being employed. In conventional practices, the intent of beaconing is to ensure that other network nodes have the highest feasible chance of receiving the beacons, so that the nodes in the ad hoc network can form neighbor relationships and transmit data through the network. As a result, beacons are typically sent at regular intervals at the highest power level possible and include a fairly large number of bits of information content.
This combination of factors, however, makes it extremely easy for an adversary to detect the beacons. The adversary may also perform direction finding on the beacon transmissions to detect the actual physical locations of the wireless network nodes. The adversary may then attempt to physically attack one or more of the nodes in the network based on information gained from detecting the beacons and determining the location of the node(s). In addition, by knowing the network layout, the adversary may be able to eavesdrop on radio transmissions in the network more easily. The adversary may then try to use this information to access confidential information from the network.
Therefore, a need exists for systems and methods that enable nodes to perform neighbor discovery with a low probability of detection.